U.S. Pat. No. 3,881,839, issued 6 May 1975 and assigned to the assignee of this invention, describes an electric fuel pump which operates submerged in fuel in a fuel tank of a motor vehicle and which includes an open-vane regenerative turbine pump. A plurality of paddle-like radial vanes on a rotating impeller of the turbine pump induce fluid flow in an annular pump channel around the periphery of the impeller. Vapor which is separated from liquid fuel in the pump channel is expelled therefrom through vapor discharge ports near the inside diameter of the pump channel. In an open-vane regenerative turbine pump in an electric fuel pump described in U.S. Pat. No. 3,418,991, issued 31 Dec. 1968 and assigned to the assignee of this invention, vapor discharges from the annular pump channel through predetermined lateral clearance between the pump housing and the sides of the impeller at the inside diameter of the pump channel. A closed-vane regenerative turbine pump described in U.S. Pat. No. 4,591,311 includes an impeller, an annular pump channel around the periphery of the impeller, a pair of abrupt steps in the pump channel on opposite sides of the impeller, and a lateral vapor port in a stagnation zone upstream of one of the abrupt steps.